Time Zones

The Earth is constantly turning on its axis. If people everywhere set their clock to the same time , midnight would be in the middle of the night on one side of the globe , but the middle of the day on the opposite side. To avoid this problem the Earth is divided into artificial time zones. These generally follow lines of the longitude that are imaginary lines running from the North to the South Pole. Some large countries, such as the USA, cover several times zones. Mainland USA is divided into Atlantic, Eastern, Central, Mountain, Pacific and Alaska zones, with Hawaii and other islands falling into further zones. Since the Greenwich Prime Meridian (0 degree) was established in 1884, there have been 24 time zones, each of 15 degree longitude and an hour apart. Those to the east are ahead of the Greenwich by an hour per zone. Those to the west are behind by one hour each. Some countries, such as India, have chosen zones halfway between those on either side, so that the whole country can use the same time.

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